A variety of radio frequency (RF), microwave and millimeter wave power amplifiers operate in conjunction with power detectors, so that the power level produced by the respective power amplifiers can be monitored and automatically adjusted/corrected, as needed. Electronic devices, such as personal computers, laptop computers, portable game devices, personal digital organizers, and the like, which provide the capability of connecting with access points of communication networks, including wireless networks, typically include power amplifiers.
Access to different types of communications networks through network access points requires compliance with the associated standards, which typically have differing frequency bands, power levels and other parameters. Increasingly, the trend is to equip electronic devices with multi-band, multi-mode capability, so that connection to a network access point from the electronic device is possible regardless of the particular standard available. For example, a portable electronic device may include wireless internet access systems for respectively communicating over multiple networks having IEEE 802.11 (WiFi) and IEEE 802.16 (WiMax) standards. These standards provide for different access parameters, including different frequency bands and power ranges.
Wireless access front end modules (FEMs) are usually designed with numerous power amplifiers for transmitting data from the electronic device to the corresponding access points. A particular power amplifier is turned on when the electronic device attempts to connect with the corresponding access point, for example, depending on the wireless access standard available at the time/location.
A power amplifier for wireless access uplink transmission, for example, is fitted with a power detector that enables the access point to control the amount of power transmitted by the electronic device through a feedback loop, consistent with maintaining the integrity of the link and conserving the electronic device's battery life (e.g., for a portable electronic device). When multi-band operation requires multiple power amplifiers, each power amplifier is fitted with a corresponding power detector optimized for use in the frequency and power ranges covered by the respective power amplifier. The outputs of the multiple power detectors are then switched or wired together in such a way that a single power detector output is provided. Also, the outputs of the power amplifiers (e.g., corresponding amplified RF signals) are selectively output from the FEM through a switch.
While this conventional method matches power detectors with respective frequency and power ranges, performance suffers because the various detectors tend to have inconsistent operational characteristics, such as voltage offset, gain and compression, making accurate system calibration difficult. Further, compromises are made in terms of cost and size, due to the redundancy of the power detector circuitry.
For example, FIG. 1 is a block diagram depicting a conventional FEM 100 having multiple power detectors configured for operation in accordance with different communication standards.
FEM 100 includes power amplifiers 110 and 120, which correspond to different frequency bands and/or power levels of the different communication standards. For example, power amplifier 110 may correspond to a WiFi access point and power amplifier 120 may correspond to a WiMax access point. A switch 130 is used to select the output of one of the power amplifiers 110 or 120 to output a corresponding RF signal.
The power amplifier 110 is connected to a first power detector 114 through coupler 112. The power detector 114 is optimized for use in the frequency range covered by the power amplifier 110 (e.g., corresponding to a WiFi access point). The power amplifier 120 is connected to a second power detector 124 through coupler 122. The power detector 124 is optimized for use in the frequency range covered by the power amplifier 120 (e.g., corresponding to a WiMax access point). Also, the detector outputs Ndet1 and Ndet2 of the power detectors 114 and 124 may be switched or tied together, as discussed above. Redundant components are required for each of the power amplifiers 110, 120, as well as each of the power couplers 112, 122 and power detectors 114, 124.